#include<iostream>
#include<unistd.h>
#include<sys/wait.h>
#include<fcntl.h>
#include<cstring>
#include<cstdio>

void ChildWrite(int wfd)
{
    char buffer[1024];
    int cnt = 0;
    while(true)
    {
        snprintf(buffer, sizeof(buffer), "I am child, pid: %d, cnt: %d", getpid(), cnt++);
        write(wfd, buffer, strlen(buffer));
        sleep(1);
    }
}

void FatherRead(int rfd)
{
    char buffer[1024];
    while(true)
    {
        buffer[0] = 0;
        // // 从管道读取数据（阻塞式调用）
        //子进程每 1 秒写一次，父进程等子进程写完就立刻读，二者因管道的阻塞特性 “间接同步”，表现为每秒刷新一次数据
        ssize_t n = read(rfd, buffer, sizeof(buffer)-1);
        if(n > 0)
        {
            buffer[n] = 0;
            std::cout << "child say: " << buffer << std::endl;
        }
    }
}




int main() 
{
    //1.创建管道
    int fds[2] ={0};
    int n = pipe(fds);
    if(n < 0)
    {
        std::cout << "pipe error" << std::endl;
        return -1;
    }
    std::cout << "fds[0]: " << fds[0] << std:: endl;
    std::cout << "fds[1]: " << fds[1] << std:: endl;

    //2.父进程写入数据创建子进程
    pid_t id = fork();
    if(id ==0)
    {
        //child
        //3.关闭子进程读端
        close(fds[0]);
        ChildWrite(fds[1]);
        close(fds[1]);
        exit(0);
    }
    //3.父进程关闭写端
    close(fds[1]);
    FatherRead(fds[0]);
    waitpid(id, nullptr, 0);
    close(fds[0]);

    return 0;
}